Q:[Paraphrased-lost the original email]"Can you explain why you think a
kibbled diet has led to more disease compared to a natural diet when wild
animals have such short lifespans?"
 
A: I could explain, but then *everyone* would know.
 
It is quite true that wild animals have a very short life span compared to
their domesticated kin.  Several different sources pinpoint the average
life span of European polecats (and New Zealand feral ferrets) at *UNDER*
one year.  Obviously, if the average life span was actually less than a
year, the species would go extinct because neither polecats nor ferrets
breed in the wild until they are at least a year old.  Wild animal
populations have an extremely high death rate for young animals, and this
is what depresses the average life span of ferrets and polecats.  There are
still individuals that live as long (or longer) than their domesticated
kin, but they are fewer in number, and proportionately fewer in certain age
classes, especially those older than a couple of years.
 
A look at number of offspring will confirm this idea.  Animals with a high
predation/death rate tend to have lots of babies per litter (like rabbits
and ferrets), while those with low predation rates tend to have low numbers
of babies (like lions and people).  The high number of young in ferret
litters is strong evidence that ferrets (or rather, polecats) have a high
death rate, and the average age of death suggests most of the animals dying
are quite young.
 
As for diseases, it is very difficult to correlate wild population disease
rates to domesticated pet disease rates because of the inherent complexity,
as well as the lack of common elements for comparison.  For example, most
wild animals do not actually die of disease, especially if you exclude
human-introduced diseases, like distemper wiping out the African hunting dog
or the black-footed ferret.  In other words, the animal is weakened by the
disease, resulting in the animal being killed and eaten by a predator, so
the lion killed the animal, not the disease.  Also, in most wild animal
populations, disease is usually associated with nutrition, and only those
animals that are malnurished contract diseases bad enough to kill them.
Now, of course this is greatly simplified; obviously there are mutations of
various diseases that run amok through wild animal populations, and some can
even cause extinction events.  But for the most part, well-fed animals have
low incidence of disease, and in a predatory environment, the sick ones are
killed and eaten before their disease load poses a major danger to the rest
of the population.
 
Pets are far more subject to disease than wild animals, because they are
generally protected from predation and because they are kept in close
proximity to each other.  In pets, the disease consumes the individual and
spreads to other close pets.  The death rate from disease in pet or
livestock populations can be staggering.  I know of an instance not long ago
were a mink farm lost more than 2000 mink to distemper; this would never
occur in the wild because mink are strict territorialists, which limits the
spread of the disease.  Also, because sick mink would be rapidedly killed
and eaten by larger predators, the disease is again limited.  My ferret
business is a prime example of this effect; I have 22 ferrets living in
close proximity to each other, and when one catches giardia, or ear mites,
or even a cold, you can be sure most of the others will follow the lead and
come down with it themselves.  This is a serious problem in many shelters,
and probably accounts for the spread of ECE and other ferret-related
diseases; ferret shows have huge numbers of ferrets in a very small place,
and can mimic cattle yards and day care centers in terms of spreading
disease.  (Those interested should search the phrase "evolutionary medicine"
for further info.)
 
There is no doubt domesticated pets have a longer average lifespan than
wild animals, but most of that difference is due to the large number of
young animals surviving to adulthood that would normally be eaten by
predators.  Pets are often treated with medicines which allow them to
survive disease, or not even contract it, and this lengthens the average
life span.  But with all of this increase in the average life span, there
is no real evidence that domestication actually increases the "real" life
span, which is the oldest age an animal can live.  In other words, while a
European polecat or New Zealand feral ferret might have an average life
span of 10 months, there are individuals that will live to the upper limits
of the ferret/polecat lifespan, about 12-14 years.  This is provable by
taking the animals out of the wild and placing them in a zoo setting, which
has been done with enough wild animals having domesticated counterparts to
prove the relationship.  Domestication doesn't necessarily increase the
average life span; medical care and lack of predation does.
 
As we are only realizing now, *diet* can shorten that increased life span
quite dramatically; heart disease, pancreatic and gastrointestinal
problems, and overnutrition can all cut short human lives, especially in a
non-exercise environment.  There is no reason to assume the same is not
true for ferrets, especially since ferrets are often used as a model of
human cardiovascular (and other) systems.  It is hard to imagine any modern
nutritionist saying the traditional western diet is healthier than the diet
our ancestors evolved consuming.  True, today's diet has higher levels of
proteins, but it also has more "bad" fat and greater levels of grain and
sugar.  The ferret faces an even greater dietary shift; one from primarily
fat and protein, to one between 60-70% grain carbohydrates.  I believe that
while kibbles are an effective diet, they are not optimal, and we should
encourage pet-food makers to better investigate the issues.
 
Bob C and 22 Mo Ferts Who Love Meeces Pieces
[Posted in FML issue 2421]